As the motor vehicle industry becomes more competitive and international in scope, it is necessary for motor vehicle manufacturers to expand the manufacturing and distribution of motor vehicle products across national boundaries. this has given rise to the design of so-called world cars in which a particular motor vehicle model is designed to be simultaneously assembled and distributed in worldwide markets while the vehicle components may be manufactured in only one or two countries.
A serious constraint on this worldwide manufacturing and marketing strategy resides in the fact that governments in various nations have different regulations governing the motor vehicles to be made or sold in that country. This is particularly the case with regard to safety equipment such as seat belt systems. As a result it is common for a manufacturer of a so-called world car to manufacture or purchase more than one type of seat belt retractor for use in a particular model of vehicle body.
Seat belt retractors commonly include a frame having a base wall for attachment to a motor vehicle structure such as a pillar. The frame also has side walls with aligned apertures to receive a shaft which rotatably mounts a belt reel. A spiral spring acts between the housing and the reel shaft to bias the reel in the direction to wind up the restraint belt. A lock bar extends between the housing side walls and is movable into engagement with a pair of sprockets carried by the belt reel to lock the reel against belt unwinding rotation.
A sensing mechanism is conventionally provided to lock up the reel by moving the lock bar into engagement with the reel sprockets. The sensing mechanism may be responsive to vehicle deceleration or to the rate of belt unwinding from the reel. The vehicle sensitive locking mechanism includes a ball or pendulum which moves relative to the lock bar upon occurrence of a vehicle deceleration condition to move the lock bar to the locked condition.
The belt sensitive locking mechanism includes a weight which is carried by the reel and lags behind rotation of the reel in response to a certain condition of belt unwinding to initiate movement of the lock bar to the locked position. The vehicle sensitive locking feature is preferred in the United States and Canada but the belt sensitive locking feature is permissible. However, in Europe, governmental regulations require the use of both a vehicle sensitive locking mechanism and a belt sensitive locking mechanism. Accordingly, it is necessary to design, tool, and inventory more than one retractor even though the vehicle in which the retractor is used is intended for worldwide manufacture and distribution.
Another feature available in seat belt retractors is a tension relief mechanism, also known as comfort mechanism, which includes a pawl and ratchet arrangement to lock the reel against rotation in the belt windup direction so that the belt is held at a slackened tension-free length about the occupant. This feature has gained wide acceptance in the United States and Canada.
Another factor contributing to the proliferation of seat belt retractor designs is that it is sometimes desirable to have the belt exit from the back side of the reel adjacent the frame base wall and then in other vehicle installation it is desirable to have the belt exit off the front side of the reel away from the base wall. For example, in those vehicles where the belt is to be hidden behind a plastic trim panel attached to the pillar, the belt exits off the back side of the reel so that the belt lies close along the pillar.
Heretofore it has been necessary to design and tool a particular seat belt retractor arrangement for each new motor vehicle, taking into account the direction of belt exit from the retractor, as well as the governmental requirements and customer preferences for each part of the world where such vehicles will be sold.
It would be desirable to provide a universally adaptable retractor which could be assembled from off-the-shelf standard components to meet the particular requirements of each new vehicle offering. Such a retractor would compress the time required for product introduction, deproliferate the parts inventory, and substantially reduce tooling costs for new vehicle models.